body {
    /* background: #f2f2f2; */
    background: #282c34;
}

.frame {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 400px;
    height: 400px;
    margin-top: -200px;
    margin-left: -200px;
    border-radius: 2px;
    box-shadow: 1px 2px 10px 0px rgba(0, 0, 0, 0.3);
    overflow: hidden;
    background: #1abc9c;
    color: #fff;
    font-family: 'Open Sans', Helvetica, sans-serif;
}

.center {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.input {
    display: none;
}

.button {
    position: relative;
    box-sizing: border-box;
    display: inline-block;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background: none;
    border: 1px solid #fff;
    color: #fff;
    cursor: pointer;
    text-align: center;
    font-size: 16px;
    font-weight: 400;
    line-height: 28px;
    transition: all 0.5s ease-in-out;

    &:hover {
        background: #16a085;
        transition: all 0.3s ease-in-out;
    }

    &:before {
        display: block;
        content: '';
        position: absolute;
        z-index: -1;
        top: -1px;
        left: -1px;
        right: -1px;
        bottom: -1px;
        border-radius: 50%;
        background: #fff;
        transform: scale(0);
        transition: all 0.5s ease-in-out;
    }
}

#input-1:checked ~ .button-1,
#input-2:checked ~ .button-2,
#input-3:checked ~ .button-3,
#input-4:checked ~ .button-4 {
    color: #1abc9c;
    background: none;
    transition: all 0.5s ease-in-out;

    &:before {
        transform: scale(1);
    }
}
